Generally, a distance between vehicles is measured to ensure safety driving and to control a safety distance between vehicles. When driving a vehicle on a road in heavy traffic congestion, a driver continues to step on or off a brake pedal while checking the distance from a leading vehicle in front thereof, and such brake manipulation causes driver fatigue. Furthermore, at high speed, the distance from the lead vehicle becomes an important safety factor.
In addition, a lead distance control system recently used for safe driving or unmanned driving also requires accurate detection of a distance between vehicles.
In the related art, radars, stereo cameras, or the like have been used to measure the distance between vehicles.
However, radars are very expensive, causing an increase in vehicle price when equipped to a vehicle. The stereo cameras are also expensive, require a very precise technique for tuning operation, and have difficulty in application to mass production of vehicles.